A chat-programm (I SEEK YOU) where you can instant message people in your list.
People first get an ICQ number
which can be send to others so that they can add you to their buddies list.
Fortunantly, there is an "AUTHORIZE" option ,
so random people can't add you if you don't want it when they found
you through the search option.

The best option is the Invisible Mode:
people can't see your online status,
except if you want them.

You can add them into your visible list. In contrast to that, there is also an Invisible-list.

ICQ makes very unsociable if you talk to many people. It's a real time killer.
Only use it for talking to friends from the realworld.

Used to be a really cool chat program in the 90s before MSNmessenger was popular and before the whole safety in cyberspace was an issue. Mostly used by perverted sex freaks who rarely made any effort to conceal their age and intentions, a fact not helped by the various types of searches like 'romance' and a search engine which revealed many users when a typical screen name like 'angel' is typed in. This chat program (i don't know about now) made an "uh oh" sound whenever the user received a message. Pretty annoying when 5 people are trying to message you at once.

Chat program full to the brim with advertisments for perkier breasts and larger penises, perverts who ask you for sex then abuse you for telling them to get fucked, and old men who have nothing better to do than call themselves "teddybear69" and contact 14 year old girls through the 'search contact' function.